Pyrolysis products from various types of plastics using TG-FTIR at different reaction temperatures

Pyrolysis products of low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), and municipal plastic waste at different reaction temperatures were predicted in the current study using a newly developed thermogravimetric analyzer coupled with Fourier transform infrared spectroscopy (TG-FTIR) method. The experiments revealed that pyrolysis products of LDPE and PP at 500 °C were almost wax. Above 600 °C, wax formed from LDPE and PP almost disappeared, while the production of light hydrocarbons was enhanced. In the cases of LDPE and PP, the benzene and toluene formations were clearly observed above 800 and 700 °C, respectively. For PS, styrene was observed as the major component at 500–800 °C. With increasing temperature, the formations of alkenes, benzene, and toluene were enhanced at the expense of styrene. Different from other plastics, PET produced a pyrolysis vapor containing mainly CO₂ and CO. FT-IR spectra of PET were almost unchanged despite increasing temperature above 600 °C. In the case of municipal plastic waste, the product distribution was similar to those of LDPE and PP. The new TG-FTIR method turned out to be an effective tool to predict pyrolysis products, especially gases products having low molecular weights.